5i'
2.2 Lining-up and monitoring of an international television
connection
It is assumed that the international television connection is
as shown in Figures 2/N.51, 5/N.51 and 6/N.51 and that such a con-
nection is provided by the interconnection of permanently and/or
occasionally established television circuits.
Recommendation N.60
NOMINAL AMPLITUDE OF VIDEO SIGNALS AT VIDEO
INTERCONNECTION POINTS
At video interconnection points, the nominal amplitude of the
picture signal, measured from the blanking level to the white level
should be 0.7 V (0.714 V for system M signals), while the nominal
amplitude of the synchronizing pulses should be 0.3 V (0.286 V for
system M signals), so that the nominal peak-to-peak amplitude of a
monochrome video signal should be 1.0 V. The addition of colour
information results in an increase in the overall amplitude of the
video signal. The magnitude of this increase depends upon the
colour system employed, but should not exceed 25% (i.e. nominal
amplitude of composite colour video signal | .25 V).
Figure 1/N.60 shows the waveform of a video signal.
Figure 1/N.60 p.
Recommendation N.61
MEASUREMENTS TO BE MADE BEFORE THE LINE-UP PERIOD
THAT PRECEDES A TELEVISION TRANSMISSION
The national television circuits should be so adjusted that,
when they are connected to the international television link, the
amplitude of the video signals at the video interconnection points
is in accordance with Recommendation N.60.
Recommendation N.62
TESTS TO BE MADE DURING THE LINE-UP PERIOD
THAT PRECEDES A TELEVISION TRANSMISSION
1 Introduction
International television circuits or national sections of such
circuits may be provided either by Administrations or broadcasting
organizations; both types of entities establish ITCs to carry out
the functions given in Recommendation N.55. One of those functions
is to test the international television circuits/links before they
are handed over to the broadcasting organizations for programme
transmission.
International television circuits are:
- circuits with terrestrial sections only
- circuits comprising a satellite section with
national circuit sections between each earth station and the ITC in
the same country.
Figure 1/N.62 shows an example of an IMDTC (International Mul-
tiple Destination Television Connection), using circuits of both
types.
2 Test signal source identification
All full field test signals as described in this Recommenda-
tion should be superimposed with an identification which includes
the point of origin and the name of the sending authority. It may
be transmitted either in monochrome or in colour according to
preference or to suit the technical requirements of the particular
test signal being transmitted. If the local language of the ori-
ginating station is not an internationally recognized language then
the idendification should be displayed not only in the local
language of the station concerned but also in one of the interna-
tionally recognized languages.
3 Test procedure
In accordance with Recommendation N.54, lining-up and testing
of the national and international circuit sections should take
place between H - 30 and H - 15 min, where H is the time at which
the circuit should be handed over to the broadcasting organization.
In practice, these tests normally take place:
- between ITCs and earth stations
- between earth stations
- between ITCs in adjacent countries linked by ter-
restrial circuits.
The use of insertion test signals (ITS) has been demonstrated
to expedite the pre-transmission line-up testing of terrestrial and
satellite circuit sections. Therefore, whenever possible, insertion
test signals in accordance with CCIR Recommendations 567 [1] and
569 [2] should be used together with appropriate automatic measur-
ing equipment during the line-up period. Insertion test signals
from the sending broadcasting organization should also be used dur-
ing the preparatory period and subsequent transmission for monitor-
ing and fault location purposes.
An example of the circuits and circuit sections to be tested
during the first half of the line-up period is shown in
Figure 1/N.62.
Priority should be given to verifying the continuity and that
the send and receive levels are correct.
Table 1/N.62 gives a suitable timetable of the sequence of
measurements to be made during the line-up period.
At H - 15 min precisely, the circuit sections are intercon-
nected to form international circuits and the international cir-
cuits interconnected to form international links which could be
multiple destination. Tests are carried out from the sending ITC
for each international link or international multiple destination
circuit. (See the example given in Figure 1/N.62.) Again, priority
is given to the continuity of each international circuit or link
and the send and received levels.
Figure 1/N.62, p.
At H precisely, or a few minutes beforehand if the
pre-transmission tests have been completed, the ITCs extend the
international circuits/links to the broadcasting organization so
that the international television connection from the sending
broadcasting organization to the receiving broadcasting
organization(s) can be verified. Any interconnections required in
the premises of the broadcasting organizations will also be made at
this time. International television connections should be made
available to the broadcasting organizations on time, even if all
tests have not been completed, provided that the continuity and
levels have been verified.
There is a need for broadcasting organizations to assess sub-
jectively the quality of the television picture as per
Table 1/N.64. If colour bar signals are used for this purpose, the
_________________________
composite signal (colour bars plus captions, etc.) must not exceed
1 volt (peak-to-peak) in order to preclude interference with adja-
cent video channels, particularly on half transponder satellite
operation.
H.T. [T1.62]
TABLE 1/N.62
Sequence of measurements
_________________________
As defined in [3].
_____________________________________________________________________________________________________________________
Items Timing Signal | ua) Measurement
_____________________________________________________________________________________________________________________
1a 1b {
H
-30 to H
-25
H
-15 to H
-10
} {
B2 or B3 and B1
(pulse and bar) or insertion test signal | ub)
} {
Luminance bar amplitude error and short period variations (1 s)
Bar tilt or base line distortion | uc)
2T pulse-to-bar ratio
}
_____________________________________________________________________________________________________________________
2a 2b {
H
-25 to H
-23
H
-10 to H
-8
} {
No input signal
or "quiet line"
} {
Signal-to-weighted-random-noise ratio | ud)
}
_____________________________________________________________________________________________________________________
3a 3b {
H
-23 to H
-21
H
-8
to H
-6
} A (field bar) {
Field-time waveform distortion
}
_____________________________________________________________________________________________________________________
4a 4b {
H
-21 to H
-19
H
-6
to H
-4
} {
Insertion test signals | ub)
} {
Chrominance-luminance gain inequality
Peak differential gain
Peak differential phase
}
_____________________________________________________________________________________________________________________
5a 5b {
H
-19 to H
-15
H
-4
to H
| ue)
} {
B2 or B3 and B1 or insertion test signals | ub)
} {
Verification of continuity and line-up
}
_____________________________________________________________________________________________________________________
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a) Signals A, B1, B2 and B3 are defined in CCIR Recommendation 567
| 1].
b) To be inserted in appropriate lines of a video signal with a
mean average picture level (APL).
c) Bar tilt or base line distortion may be measured by mutual
agreement of the Administrations concerned.
d) Where an ITC has equipment for measuring the
signal-to-weighted-noise ratio on the "quiet" line it should take
that measurement during the first five minutes of the test sequence
if insertion test signals are received.
e) In accordance with Recommendation N.54 connection may be made to
the broadcaster by an ITC during this period. Connection may also
be made to the sending broadcaster provided the sending ITC is
receiving a video signal from the broadcaster originating the
transmission.
Table 1/N.62 [T1.62], p.
4 Tests to be made by the ITCs
Only 15 minutes is allowed for each of the series of tests
referred to in S 2. This period is more than adequate if modern
test equipment is used. The measurements to be carried out are
defined in CCIR Recommendations 567 [1] or 569 [2].
Before the commencement of the line-up period the staff of the
ITCs should ensure that the test generator(s) and measuring equip-
ment are in good working order. It is particularly important that
impeccable test signals should be sent so as to prevent receiving
ITCs from concluding, on the basis of their measurements, that a
circuit is faulty when that is not the case.
If difficulty is experienced in performing the required tests,
as a minimum, the circuit continuity should be established and the
send and received levels checked, with the assistance of the send-
ing broadcasting organization. If colour bar signals are used for
this continuity check, the amplitude should be checked and applica-
tion must be in accordance with S 3.
Table 2/N.62 lists the parameters and test objectives for
international television circuits/links.
H.T. [T2.62]
TABLE 2/N.62
Test objectives
| ua)
_____________________________________________________________________________________________________________________________________________________________________________________________________________________
{
{
Circuit sections
Full transponder 525-line 625-line 525-line|
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625-line |
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_____________________________________________________________________________________________________________________________________________________________________________________________________________________
(1) (2) (3a) (3b) (4) (5)
_____________________________________________________________________________________________________________________________________________________________________________________________________________________
Luminance bar amplitude error {
_ 0.5 dB
or 5 |
or 5 IRE units
} {
_ 0.25 dB
or 2.5 | or
2.5 IRE units
} {
_ 0.25 dB
or 2.5 | or
2.5 IRE units
} {
_ 1 dB
or 11 |
or 11 IRE units
} {
_ 1 dB
or 11 |
or 11 IRE units
}
_____________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Short period variations of luminance bar error (1 s)
} {
_ 0.3 dB
or 3 |
or 3 IRE units
} {
_ 0.1 dB or
1 | or
1 IRE unit
} {
_ 0.1 dB or
1 | or
1 IRE unit
} {
_ 0.3 dB
or 3 |
or 3 IRE units
} {
_ 0.4 dB
or 4 |
or 4 IRE units
}
_____________________________________________________________________________________________________________________________________________________________________________________________________________________
Bar tilt _ 1 | _ 1.5 | _ 1 | _ 1 | _ 3 | _ 2 | |
|
_ 4 |
_____________________________________________________________________________________________________________________________________________________________________________________________________________________
Base ligne distortion _ 1 | Note Note _ 1 | _ 3 | Note
_____________________________________________________________________________________________________________________________________________________________________________________________________________________
2T pulse-to-bar ratio _ 6 | _ 6 | _ 6 | _ 6 | _ 8 | |
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_ 12 | |
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_ 10 |
_____________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Signal-to-weighted-random-noise ratio
} 56 dB 49 dB 54 dB 56 dB 48 dB
_____________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Field time waveform distortion
} _ 2 | _ 2 | _ 1 | _ 2 | _ 6 | _ 4 | _ 6 |
_____________________________________________________________________________________________________________________________________________________________________________________________________________________
{
Chrominance-luminance gain inequality
} _ 10 | _ 10 | _ 10 | + 8 | - 11 | _ 10 | + 12 | - 20 | |
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_ 15 |
_____________________________________________________________________________________________________________________________________________________________________________________________________________________
Peak differential gain _ 10 | _ 10 | _ 10 | _ 10 | _ 8 | _ 15 |
_____________________________________________________________________________________________________________________________________________________________________________________________________________________
Peak differential phase _ 3 _ 4 _ 3 _ 3 _ 5 _ 6 {
_ 8
a)
In principle, the test objectives for terrestrial circuits/links apply to those having a length of about 1250 km.
}
_____________________________________________________________________________________________________________________________________________________________________________________________________________________
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b) Test objectives given in columns 3a, 3b and 5 refer to temporary
circuit sections and circuits provided by INTELSAT satellites and
relate to expected performance in global beam utilizing earth sta-
tions having G/T of 40.7 dB/K and elevation angles of 10. Different
figures may be appropriate when other satellites, earth station
sizes and elevation angles are employed.
Note - Under study.
Table 2/N.62 [T2.62], p.
References
[1] CCIR Recommendation Television performance of televi-
sion circuits designed for use in international connections ,
Rec. 567, Vol. XII, ITU, Geneva, 1986.
[2] CCIR Recommendation Definitions of parameters simpli-
fied for automatic measurement of television insertion test signals
, Rec. 569, Vol. XII, ITU, Geneva, 1986.
[3] EBU (European Broadcasting Union) Video measurement and
the correction of video circuits , Technical Monograph 3116 (L.E.
Weaver, 1978), Appendix 3, Sections 5, 6, 7 and 8.
Recommendation N.63
TEST SIGNALS TO BE USED BY THE BROADCASTING ORGANIZATIONS
DURING THE PREPARATORY PERIOD
After the broadcasting organizations have taken over the
international television connection, they may decide to make meas-
urements on the complete connection from the point where the telev-
ision programme is produced to the point or points where it is to
be received.
The broadcasting organizations often use live pictures for
testing during the preparatory period, especially when a standards
convertor is involved. If for any reason they should need to send
test signals then it is desirable that the telecommunication
Administrations should recommend the broadcasting organizations in
their countries to send signals that are in accordance with those
recommended in Recommendation N.67 (at levels in accordance with
Recommendation N.60), so that the staff at intermediate video
interconnection points can, if necessary, compare the results of
the measurements made by the broadcasting organizations with those
obtained by the telecommunication Administrations during the
line-up period. There is no occasion to readjust the output levels
of the station equipment since these have already been set during
the line-up period.
All test signals transmitted prior to the actual television
transmission, being full field or otherwise, should be superimposed
with the identification of the broadcaster and location from where
the test signal is originating. This identification may be
transmitted either in monochrome, or in colour, according to
preference or to suit the technical requirements of the particular
test signal being transmitted. If the local language of the
originating source is not an internationally recognized
language then the identification signal should be displayed not
only in the local language of the country concerned but also in one
of the internationally recognized languages.
When a full field signal is transmitted simply as a means to
check link or tandem connection continuity, it may comprise any
suitable composite video signal (such as test pattern, pulse/bar or
other suitable picture or pattern) provided that it contains
specific signal components that include Peak White, synchronizing
pulses and the identification signal (as previously described) of
the station or broadcaster transmitting the signal. The composite
signal (colour bars plus captions, etc.) must not exceed 1 volt
(peak-to-peak) in order to preclude interference with adjacent
video channels, particularly on half transponder satellite opera-
tion.
When television pictures which contain electronically
generated components, e.g. captions, are used, the
out-of-band-spectral power in any 4 kHz band above 1.2 times the
nominal video bandwidth shall not exceed -50 dB.
Recommendation N.64
QUALITY AND IMPAIRMENT ASSESSMENT
1 5-grade scale for quality and impairment assessment
The 5-grade scale, applicable to both quality and impairment
assessments in Table 1/N.64 should be used.
H.T. [T1.64]
TABLE 1/N.64
__________________________________________________
Grade Quality Impairment
__________________________________________________
5 Excellent Imperceptible
4 Good Perceptible but not annoying
3 Fair Slightly annoying
2 Poor Annoying
1 Bad Very annoying
__________________________________________________
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Table 1/N.64 [T1.64], p.
Although the scale is intended, in connection with television,
to apply to overall picture assessment, it should be noted that the
same scale could be used for a critical assessment of particular
picture characteristics. Moreover, the number of the grade can be
taken as either a quality assessment or an impairment assessment.
Depending on the context, for example, a Grade 3 picture is of
fair quality, having slightly annoying impairments. The same scale
can be used in the case of types of transmission other than televi-
sion.
Note 1 - It is implicit that before a circuit is handed over
to a broadcasting organization all reasonable steps will have been
taken to ensure that the circuit quality from the point of view of
transmission is the best that can be achieved at the beginning of
the preparatory period.
Note 2 - Grade 1 should be applied only to a transmission
considered to be unusable by the broadcasting organization con-
cerned. If, under exceptional circumstances, the broadcasting
organization decides to use a transmission so graded, because of
the interest in the information to be transmitted, this should not
constitute a precedent for changing the grade or for changing the
significance of Grade 1.
Note 3 - This Recommendation does not apply to the assessment
of speech transmission quality in telephony.
Recommendation N.67
MONITORING TELEVISION TRANSMISSIONS .
USE OF THE FIELD BLANKING INTERVAL
1 Monitoring points
Technical control by the telecommunication Administrations of
a television transmission in progress should be possible at any
time:
- at national and international television centres
in the connection;
- at the last staffed-station immediately preceding
the frontier of each country and at a point in the station which
will include as much as possible of the station equipment in the
direction of transmission concerned (by providing
monitoring-demodulators if necessary).
These centres and stations should be equipped with an oscillo-
scope (the horizontal sweep frequency of which is synchronized to
the line frequency) for monitoring the electrical signal and a
picture-monitor for monitoring the complete picture.
2 Numbering of lines in a television field
For 625-line systems the numbering of the lines is as follows:
Line 1 starts at the instant indicated by 0vin Figure 2-1 of
CCIR Report 624 [1]; at this instant, the leading edge of the line
synchronization pulse coincides with the beginning of the sequence
of field synchronization pulses. The lines are numbered according
to their sequence in time, so that the first field comprises
lines 1 to 312 as well as the first half of line 313, whereas the
second field comprises the second half of line 313 and lines 314
to 625.
For 525-line systems the numbering of the lines is as follows:
Line 1 of field 1 is the line starting with the first equaliz-
ing pulse at the instant indicated by 0E\d1in Figure 2-3a of
CCIR Report 624 [2], line 1 of field 2 is the line starting with
the second equalizing pulse at one half-line period after the
instant indicated by 0E\d2in Figure 2-3b of this report [3].
3 625-line insertion test signals (ITS)
The advent of colour has caused the CCIR to recommend a
comprehensive set of test signals which may be inserted on
lines 17, 18, 330 and 331 for international monochrome or colour
transmissions This signal is illustrated in Figure 1/N.67 and is
made up as follows:
Line 17
A 10 us white bar (B2), a 2 T sine-squared pulse (B1), a
20 T composite pulse (F) and a 5-riser staircase (D1).
Line 18
A multiburst (C2) preceded by a reference bar signal (C1)
Line 330
A 10 us white bar (B2), a 2 T sine-squared pulse (B1) and
a 5-riser staircase with superimposed colour subcarrier (D2).
Line 331
A chrominance bar signal (G1) or a three-level chrominance
signal (G2), followed by a sub-carrier reference bar (E).
Figure 1/N.67 p.
4 525-line insertion test signal (ITS)
For colour the CCIR has recommended a comprehensive set of
test signals which may be inserted on lines 17 of both fields
(lines 17 and 280 if numbered consecutively) for international
monochrome or colour transmissions. These signals are illustrated
in Figure 2/N.67, c ) and d ) and are made up as follows:
_________________________
As an interim measure some organizations may decide to
omit some of the waveforms, but in this case care must
be taken not to alter the mean values appreciably.
A colour burst is present in the line blanking period
during colour transmissions. In the case of PAL colour
transmissions the chrominance subcarrier of the inser-
tion signals is locked at 60 from the (B-Y) axis.
Figure 2/N.67, c): | a luminance bar (reference white
level) (B2), a 2 T sine-squared pulse (B1), a modulated 12.5 T
sine-squared pulse (F) and a superimposed 5-riser staircase (D2);
Figure 2/N.67, d): | a reference bar signal (C1), a lumi-
nance pedestal, a multiburst signal superimposed on the
pedestal (C2) and a superimposed 3-level chrominance signal (G).
A detailed description of these signals is given in CCIR
Recommendation 473 [4].
FIGURE 2/N.67 p.
5 Measurements on insertion test signals (ITS)
In order to carry out measurements on an insertion test sig-
nal, stations and centres should also be equipped with a line
selector which enables only the test signal line (or lines) to be
displayed on the oscilloscope.
Measurements which can be made with the above signals are
given in Tables 1/N.67 and 2/N.67.
H.T. [T1.67]
TABLE 1/N.67
625-line monochrome or colour signal (Figure 1/N.67)
(CCIR Recommendation 473 | 4])
_______________________________________________________________________________
Characteristics measured Waveform used Line number
_______________________________________________________________________________
Linear distortions
Insertion gain B 2 17 and 330
Amplitude/frequency response C 2 and C 1 18
{
Line-time waveform distortion
} B 2 17 and 330
{
Short-time waveform distortion
}
- step response B 2 17 and 330
- pulse response B 1 17 and 330
{
Chrominance-luminance gain inequality
} B 2 and G 1 or G 2 17 and 330, 331
. B 2 and F 17
{
Chrominance luminance delay inequality
} F 17
_______________________________________________________________________________
{
Nonlinear distortions
}
{
Luminance line-time nonlinearity
} D 1 17
Chrominance nonlinearity G 2 331
{
Luminance chrominance intermodulation
}
- differential gain D 2 330
- differential phase D 2 and E 330, 331
{
Chrominance luminance intermodulation
} B 2 and G 1 or G 2 17, 331
_______________________________________________________________________________
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TABLE 1/N.67 [T1.67], p.
H.T. [T2.67]
TABLE 2/N.67
525-line monochrome or colour signal (Figure 2/N.67)
________________________________________________________________________________
Characteristics measured Waveform used Line number
________________________________________________________________________________
Linear distortions
Insertion gain B 2 17/field 1
Amplitude/frequency response B 2 | ua) and C 2 17 fields 1 and 2
{
Line-time waveform distortion
} B 2 17/field 1
{
Short-time waveform distortion
}
- step response B 2 17/field 1
- pulse response B 1 17/field 1
{
Chrominance/luminance gain inequality
} B 2 and F 17/field 1
{
Chrominance/luminance delay inequality
} F 17/field 1
________________________________________________________________________________
{
Nonlinear distortions
}
{
Line-time luminance nonlinearity
} D 1 | ub) 17/field 1
Chrominance nonlinearity G 17/field 2
{
Luminance/chrominance intermodulation
}
- differential gain D 2 17/field 1
- differential phase D 2 17/field 1
{
Chrominance/luminance intermodulation
} G 17/field 2
________________________________________________________________________________
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a) C 1 (line 17/field 2) may be used in place of B 2, when
line-time distortion is suitably small.
b) D 2 may be used when the chrominance/luminance intermodulation
is suitably small.
TABLE 2/N.67 [T2.67], p.
6 Insertion and removal of test signals in the field blanking
period
6.1 International signals
The appropriate international signals inserted by the ori-
ginating broadcasting organization should be transmitted to the
point of destination of the television connection. Exceptionally,
if the connection includes a standards or colour systems convertor
which does not pass signals occurring during the field blanking
period, then the signals should be monitored at the upstream video
point nearest to the convertor and new international signals, to
the appropriate standard, should be inserted at the downstream
point nearest to the convertor. The test signals should be avail-
able at any video connection point in order to facilitate assess-
ment of performance. They may also be of use in carrying out any
necessary readjustment of correctors at the final destination.
6.2 National signals
Any test signals inserted in lines 18 to 20 (525-line sys-
tems), or 19 to 21 (625-line systems) and the corresponding lines
in the second field in either standard, should be regarded as
national signals and should be removed at a suitable video point
within the national frontier so that downstream countries on the
circuit may use these lines for their own needs. Exceptionally,
and subject to agreement between all the countries concerned,
national signals may be transmitted across international frontiers.
7 General implementation
It is requested that Administrations of countries where
national broadcasting organizations have the sole right of
transmitting television signals should approach those organizations
in order that the principles of this Recommendation may be applied
as widely as possible.
Attention is drawn to the comments in Annex III to Part C of
CCIR Recommendation 567 [5]. Particular attention is drawn to the
unrepresentative result of measurements made on a single test line
per field when
half-field-rate dispersal waveforms are applied to the signal,
e.g., on satellite circuits. Comment is also made in this reference
to the difference between measurements made with full field test
signals in accordance with CCIR Recommendation 567 [5] and measure-
ments made automatically in accordance with CCIR Recommenda-
tion 569 [6].
References
[1] CCIR Report Characteristics of television systems ,
Vol. XI, Report 624, p. 5, Figure 2-1, ITU, Geneva, 1986.
[2] Ibid. , p. 7, Figure 2-3a.
[3] Ibid. , p. 7, Figure 2-3b.
[4] CCIR Recommendation Insertion of test signals in the
field-blanking
interval of monochrome and colour television , Vol. XII, Rec.
473, ITU, Geneva, 1986.
[5] CCIR Recommendation Television performance of televi-
sion circuits designed for use in international connections ,
Vol. XII, Rec. 567, ITU, Geneva, 1986.
[6] CCIR Recommendation Definitions of parameters simpli-
fied for automatic measurement of television insertion test signals
, Vol. XII, Rec. 569, ITU, Geneva, 1986.
BLANC
2.3 Maintenance of leased circuits for television transmission
Recommendation N.73
MAINTENANCE OF PERMANENT INTERNATIONAL
TELEVISION CIRCUITS, LINKS AND CONNECTIONS
1 Introduction
In most cases, circuits used for television transmissions are
provided by the Administrations, although in some countries broad-
casting organizations own all or part of the circuits within
national boundaries.
The routine maintenance of circuits used for transmissions
between two or more countries requires the closest cooperation
between the Administrations/broadcasting organizations that provide
the circuit sections.
It is recommended that routine maintenance measurements be
carried out each month on permanently installed terrestrial cir-
cuits.
This Recommendation applies also for routine test transmission
over leased satellite circuits for television transmissions
directed to TVROs not related to an ITC.
2 Test signal elements
Diagrams of the different test-signal elements as defined in
CCIR Recommendation 567 [1] are given in Annex A; the titles of
those test-signal elements with the reference designations are
given below:
Field bar Signal A Figures A-1/N.73 and A-2/N.73
Sine-squared pulse Signal B1
Figures A-3/N.73 and A-4/N.73
Luminance bar Signal B2 or, B3
Figures A-3/N.73 and A-4/N.73
Multiburst Signal C Figures A-5/N.73 and
A-6/N.73
Staircase Signal D1 and D2 Figures A-7/N.73
and A-8/N.73
Composite pulse Signal F Figures A-9/N.73
and A-10/N.73
Chrominance bar Signal G1 (625-lines only)
Figure A-11/N.73
Three level chrominance bar Signal G2 (625-lines
only) Figure A-11/N.73
Three level chrominance bar Signal G (525-lines
only) Figure A-12/N.73
3 Test equipment
3.1 Generators
CCIR Recommendation 473 [2] defines the insertion test signals
required for measurement purposes. The assembly of test signal ele-
ments in test lines is also referred to in Recommendation N.67 and
most modern test signal generators can originate the test signals,
either as insertion test signals or as full-field test signals. In
the latter mode measurements can be carried out at standard values
of average picture level (APL).
The assembly of test signal elements in the test lines is suf-
ficient for the measurement of the large majority of television
circuit parameters, that is, distortions occurring at line fre-
quency and above. However, additional test signals are needed for
low and very low-frequency measurements. A field bar is required
for the measurement of field time distortions and, for the measure
ment of long-time waveform distortion, a signal is required
which is switched at intervals of a few seconds between low and
high APLs. (For further details see CCIR Report 636 [3].)
3.2 Measurement equipment
The measurement equipment may consist of:
- an oscilloscope or television waveform monitor
with additional equipment for making nonlinearity
measurements ;
- modern television waveform monitors equipped with
line-selection and means for measuring nonlinearity distortion;
- automatic measurement equipment.
4 Measurement definitions
CCIR Recommendations 567 [1] and 569 [4] define the measure-
ments that may be made on television circuits. There are slight
differences in the way certain similar parameters are defined, for
example, insertion gain and luminance bar amplitude, and differ-
ences in the way the results are expressed, for example, luminance
bar amplitude and luminance bar amplitude error. To standardize
routine maintenance measurements, it is recommended that the defin-
itions given in Recommendation 569 [4] be used for maintenance pur-
poses whenever possible. The results are then easier to analyze
because the result of a measurement is zero for an undistorted
parameter.
5 Access points
Measurements are taken at television signal access points
which are well-defined points associated with the input and output
of a television circuit. To suit the characteristics of the meas-
urement equipment, the standard level/impedance at the access point
should be 1 volt peak-to-peak into 75 ohms. The return loss at the
access point shall be better than 30 dB.
The access point may be the point of interconnection or may be
connected to it by a distortion-free circuit having zero loss or
gain.
For flexibility, and to ensure that measured parameters are
comparable to transmission parameters, it is necessary that the
interconnection system in the ITC should handle programme and test
signals in the same way. Figure 1/N.73 shows one method of realiz-
ing that objective.
_________________________
A line selector for selecting insertion test lines for
display with older type waveform monitors or oscillo-
scopes is commercially available.
Figure 1/N.73, p.
6 Routine verification of test equipment
To ensure that test equipment errors will not lead to
incorrect adjustment of a television circuit, the test equipment
should be verified regularly.
The connection between the test signal generator and the meas-
urement equipment, via the interconnection system, should be veri-
fied at intervals of, say, three months and the results should be
within the limits given in Table 1/N.73.
H.T. [T1.73]
TABLE 1/N.73
Limits for measurement chains
________________________________________________________________
Parameter Limits
________________________________________________________________
Luminance bar amplitude error _ 1 |
________________________________________________________________
Bar tilt/Base line distortion _ 1 |
________________________________________________________________
2T pulse/bar ratio error _ 2 |
________________________________________________________________
Peak differential gain _ 1 |
________________________________________________________________
Peak differential phase _ 1
________________________________________________________________
{
Chrominance/luminance gain inequality
} _ 2 |
________________________________________________________________
{
Chrominance/luminance delay inequality
} _ 5 ns
________________________________________________________________
{
Signal-to-continuous-noise ratio (unified weighted)
} _" 65 dB
________________________________________________________________
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Table 1/N.73 [T1.73], p.
7 Maintenance limits
The figures given in Table 2/N.73 showing the maintenance lim-
its are based on the design objectives for hypothetical reference
circuits given in CCIR Recommendation 567 [1] but refer to interna-
tional television circuits, nominally one-third of the length of
the hypothetical reference circuit, between terminal ITCs which are
normally in adjacent countries. These limits are expected to apply
for most of the time but may be exceeded for part of the time.
Hence, maintenance staff must exercise judgement on the action to
be taken when a circuit is outside the maintenance limits for any
parameter. If the results are well outside the limits, for example,
if the error is greater than twice the limit value or the
signal-to-noise ratio is 3 dB worse than the limit value, the fault
should be located and corrected. On the other hand, if the limits
are only exceeded by a relatively small amount, corrective action
should not be carried out unless a given parameter exceeds the
maintenance limits in two successive months.
Maintenance limits for circuit sections which are different in
length and construction from the circuit section equal to one third
of the hypothetical reference circuit may be derived by the appli-
cation of the Laws of Addition specified in CCIR Recommenda-
tion 567 [1] to the limits quoted in Table 2/N.73, but the precau-
tions in S 10 should be noted.
BLANC
H.T. [1T2.73]
TABLE 2/N.73
Maintenance limits for permanent international television circuits
__________________________________________________________________________________________________________________________________
Item (Note 12) Parameter Test waveform(s) Maintenance limits
__________________________________________________________________________________________________________________________________
525 625
__________________________________________________________________________________________________________________________________
1 {
Luminance bar-error
(Note 1)
} B2 or B3 _ 11 IRE units _ 11 | (_ 1 dB)
__________________________________________________________________________________________________________________________________
2 {
Variation of luminance bar-error
(e.g. 1 s)
} B2 or B3 _ 3 IRE units _ 2 | (_ 0.2 dB)
__________________________________________________________________________________________________________________________________
3 {
Variation of luminance bar-error
(e.g. 1 hour)
} B2 ou B3 _ 8 IRE units _ 11 | (_ 1 dB)
__________________________________________________________________________________________________________________________________
4 {
Signal-to-continuous-weighted-noise ratio
} {
No input signal
(Notes 1, 3)
or
"quiet" line
(Notes 2, 4)
} _" 56 dB _" 52 dB (Note 10) |
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__________________________________________________________________________________________________________________________________
5 {
Signal-to-periodic-noise ratio (power supply frequency
-0.1 kHz)
(Note 2)
} No input signal _" 35 dB (Note 5)
__________________________________________________________________________________________________________________________________
6 {
Signal-to-periodic-noise ratio (1 kHz - f
)
(Note 2)
} No input signal _" 55 dB
__________________________________________________________________________________________________________________________________
7 {
Signal to impulsive noise ratio
(Note 2)
} No input signal _" 25 dB
__________________________________________________________________________________________________________________________________
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3 | 10 | {
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4 | 7 | {
__________________________________________________________________________________________________________________________________
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4 5 {
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_ 10 | _ 8 | {
__________________________________________________________________________________________________________________________________
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_ 3 _ 5 (Note 6)
__________________________________________________________________________________________________________________________________
13 {
Chrominance-luminance intermodulation
(Notes 1, 2)
} G or G2 _ 3 | (Note 6)
__________________________________________________________________________________________________________________________________
14 {
Sync. amplitude error
(Note 1)
} (Note 7) _ 10 | (Note 6)
__________________________________________________________________________________________________________________________________
15 {
Long-time waveform distortion
(Note 2)
} "Bump" signal {
40 |
(Notes 13, 14)
H.T. [2T2.73]
}
__________________________________________________________________________________________________________________________________
{
TABLE 2/N.73 (cont.)
}
Item (Note 12) Parameter Test waveform(s) Maintenance limits
__________________________________________________________________________________________________________________________________
16 {
Field-time waveform distortion
(Note 2)
} A (Note 11) _ 2 | _ 6 |
__________________________________________________________________________________________________________________________________
17 {
Line-time waveform distortion (Note 2)
Bar tilt (Note 1)
} B2 or B3 _ 1 | _ 3 |
__________________________________________________________________________________________________________________________________
18 {
Base line distortion (Note 1)
} B2 or B3 _ 1% _ 3%
__________________________________________________________________________________________________________________________________
19 {
2T pulse/bar ratio error (Note 1)
} B1 and B2 or B3 _ 6 | _ 8 |
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__________________________________________________________________________________________________________________________________
20 {
Short-time waveform distortion
(Note 2)
} B1 {
1st adjacent lobe
6 |
2nd adjacent lobe
3 |
}
__________________________________________________________________________________________________________________________________
21 {
Gain/frequency characteristic
(Note 2)
} C (Note 8) _ 1 dB +1.5 dB to -1 dB
__________________________________________________________________________________________________________________________________
22 {
Chrominance-luminance gain inequality
(Note 1)
} B2 or B3 and G, G 2 or F _ 10 | _ 10 | |
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__________________________________________________________________________________________________________________________________
23 {
Chrominance-luminance delay inequality
(Note 1)
} F _ 80 ns (Note 9)
__________________________________________________________________________________________________________________________________
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Note 1 - As defined in CCIR Recommendation 569 [4].
Note 2 - As defined in CCIR Recommendation 567 [1].
Note 3 - Noise measured via unified weighting filter and low and
high pass filters specified in Annex II to Part C of CCIR Recommen-
dation 567 [1].
Note 4 - Noise measured on line(s) allocated for noise measurement
with weighting network and filters as given in Note 3 plus a chrom-
inance frequency notch filter as specified in CCIR Recommenda-
tion 569 [4].
Note 5 - The maintenance limits refer to circuits without clamps.
When clamps are used the maintenance limits are _" 50 dB.
Note 6 - Measured at APLs of 10% and 90%.
Note 7 - Video signal containing synchronizing signals with normal
amplitude.
Note 8 - Measurements on C2 may be referred to C1 taking account
of any difference in the amplitude of the two elements. The results
of this test may conflict with those obtained with test waveforms.
If this occurs the waveform results should be considered to be
definitive.
Note 9 - The value is positive if the luminance component leads
the chrominance component.
Note 10 - Further data is required to consider amendment to this
figure.
Note 11 - A window signal is specified in CCIR Recommendation 567
[1] for use on 525-line systems. Test results are required before
limits for this signal can be included. Use of this signal should
be noted in the measurement results.
Note 12 - Routine measurements made at regular intervals may be
limited to less than the complete list of items given in
Table 2/N.73 by agreement between the Administrations concerned.
Note 13 - The value is provisional and for further study.
Note 14 - The maintenance limit applies to testing a circuit
without clamping. This is the preferred method of measurement. When
clamps are used, the maintenance limit is 6%.
Table 2/N.73 [1T2.73], p.
H.T. [2T2.73]
TABLE 2/N.73 (cont.)
________________________________________________________________________________________________________________
Item (Note 12) Parameter Test waveform(s) Maintenance limits
________________________________________________________________________________________________________________
16 {
Field-time waveform distortion
(Note 2)
} A (Note 11) _ 2 | _ 6 |
________________________________________________________________________________________________________________
17 {
Line-time waveform distortion (Note 2)
Bar tilt (Note 1)
} B2 or B3 _ 1 | _ 3 |
________________________________________________________________________________________________________________
18 {
Base line distortion (Note 1)
} B2 or B3 _ 1% _ 3%
________________________________________________________________________________________________________________
19 {
2T pulse/bar ratio error (Note 1)
} B1 and B2 or B3 _ 6 | _ 8 | |
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________________________________________________________________________________________________________________
20 {
Short-time waveform distortion
(Note 2)
} B1 {
1st adjacent lobe
6 |
2nd adjacent lobe
3 |
}
________________________________________________________________________________________________________________
21 {
Gain/frequency characteristic
(Note 2)
} C (Note 8) _ 1 dB +1.5 dB to -1 dB
________________________________________________________________________________________________________________
22 {
Chrominance-luminance gain inequality
(Note 1)
} B2 or B3 and G, G 2 or F _ 10 | _ 10 | |
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________________________________________________________________________________________________________________
23 {
Chrominance-luminance delay inequality
(Note 1)
} F _ 80 ns (Note 9)
________________________________________________________________________________________________________________
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Note 1 - As defined in CCIR Recommendation 569 [4].
Note 2 - As defined in CCIR Recommendation 567 [1].
Note 3 - Noise measured via unified weighting filter and low and
high pass filters specified in Annex II to Part C of CCIR Recommen-
dation 567 [1].
Note 4 - Noise measured on line(s) allocated for noise measurement
with weighting network and filters as given in Note 3 plus a chrom-
inance frequency notch filter as specified in CCIR Recommenda-
tion 569 [4].
Note 5 - The maintenance limits refer to circuits without clamps.
When clamps are used the maintenance limits are _" 50 dB.
Note 6 - Measured at APLs of 10% and 90%.
Note 7 - Video signal containing synchronizing signals with normal
amplitude.
Note 8 - Measurements on C2 may be referred to C1 taking account
of any difference in the amplitude of the two elements. The results
of this test may conflict with those obtained with test waveforms.
If this occurs the waveform results should be considered to be
definitive.
Note 9 - The value is positive if the luminance component leads
the chrominance component.
Note 10 - Further data is required to consider amendment to this
figure.
Note 11 - A window signal is specified in CCIR Recommendation 567
[1] for use on 525-line systems. Test results are required before
limits for this signal can be included. Use of this signal should
be noted in the measurement results.
Note 12 - Routine measurements made at regular intervals may be
limited to less than the complete list of items given in
Table 2/N.73 by agreement between the Administrations concerned.
Note 13 - The value is provisional and for further study.
Note 14 - The maintenance limit applies to testing a circuit
without clamping. This is the preferred method of measurement. When
clamps are used, the maintenance limit is 6%.
Table 2/N.73 (cont.) [2T2.73], p.
8 Schedule for routine maintenance measurements
The performance of routine maintenance measurements between
two ITCs requires adherence to routine procedures and a due regard
to the allocated time. Tests (Table 3/N.73) should start at a
scheduled time (Z ) which has been agreed between the
Administrations/broadcasting organizations concerned and should
progress in accordance with the fixed timetable. This will give
adequate time for measurements to be repeated if there is a possi-
bility that one or more circuit parameters are outside tolerance
limits.
It is necessary for the maintenance staff to book the routine
maintenance period with the programme booking centre (PBC) on a
regular basis so that the PBC can intervene when bookings are made
for programme transmissions at the same time, and propose a dif-
ferent period for the routine maintenance measurements.
The test schedule shown in Table 3/N.73 should be used by the
sub-control station at the sending end of the circuit unless there
is a specific agreement between the Administrations/broadcasting
organizations concerned to use a different test schedule.
H.T. [T3.73]
TABLE 3/N.73
Schedule for routine maintenance measurements
___________________________________________________________________________________
Duration Operation Signal
___________________________________________________________________________________
{
Z
to Z
+ 5 min
} Check level B2 or B3
___________________________________________________________________________________
{
Z
+ 5 to Z
+ 10 min
} {
Measurement of linear distortions (APL low)
} Test lines
___________________________________________________________________________________
{
Z
+ 10 to Z
+ 15 min
} {
Measurement of nonlinear distortions (APL low)
} Test lines
___________________________________________________________________________________
{
Z
+ 15 to Z
+ 20 min
} {
Measurement of nonlinear distortions (APL high)
} Test lines
___________________________________________________________________________________
{
Z
+ 20 to Z
+ 25 min
} Measurement of noise None
___________________________________________________________________________________
{
Z
+ 25 to Z
+ 30 min
} {
Measurement of field-time waveform distortion
} A
___________________________________________________________________________________
{
Z
+ 30 to Z
+ 35 min
} {
Measurement of long-time waveform distortion
} "Bump"
___________________________________________________________________________________
{
Z
+ 35 to Z
+ 95 min
} {
Variation of luminance bar amplitude
} B2 or B3
___________________________________________________________________________________
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Note - Z is the agreed time to commence the tests.
Table 3/N.73 [T3.73], p.
9 Maintenance of international television circuits
In general the programme booking centre (PBC) will not know
when permanent connections are in use for programme transmissions
and the agreement of the customer must be obtained before such con-
nections are interrupted in ITCs to carry out maintenance on a cir-
cuit.
10 Maintenance of international television circuits, links and
connections
International television circuits, links and connections will
comprise chains of circuit sections, both national and interna-
tional, connected in tandem, which are maintained and may be leased
as separate entities. Each of these circuit sections may have suit-
able maintenance limits derived as quoted in S 7.
The Laws of Addition may also be used to derive expected per-
formance limits for such chains but precautions are necessary in
the use of such limits for maintenance purposes. It is possible
that the overall response of the circuit, link or connection may
fail to meet the calculated performance expected, even though the
response of each circuit section comprising the chain meets the
individual maintenance limits used for the calculation of the
overall response. In such cases the calculated response of the
chain can only be used as a guide to the expected overall response
on the initial lining up, unless additional overall equalizers are
employed.
There is also the possibility that the difference between the
actual and the calculated overall response of the chain can vary
with time, even though the responses of the individual circuit sec-
tions remain within their respective maintenance limits.
ANNEX A
(to Recommendation N.73)
Test signal elements
An indication of the signal elements required to carry out the
tests mentioned in this Recommendation is given below in the form
of figures. Preferred assemblies for insertion test signals are
given in Recommendation N.67.
Figure A-1/N.73, p.
Figure A-2/N.73, p.
Figure A-3/N.73, p.
Figure A-4/N.73, p.
Figure A-5/N.73, p.
Figure A-6/N.73, p.
Figure A-7/N.73, p.
Figure A-8/N.73, p.
Figure A-9/N.73, p.
Figure A-10/N.73, p.
Figure A-11/N.73, p.
Figure A-12/N.73, p.
References
[1] CCIR Recommendation Television performance of televi-
sion circuits designed for use in international connections,
Vol. XII, Rec. 567, ITU, Geneva, 1986.
[2] CCIR Recommendation Insertion of test signals in the
field blanking interval of monochrome and colour television sig-
nals, Vol. XII, Rec. 473, ITU, Geneva, 1986.
[3] CCIR Report Long-time waveform distortion in long dis-
tance television circuits, Vol. XII, Rec. 636, ITU, Geneva, 1986.
[4] CCIR Recommendation Definitions of parameters simpli-
fied for automatic measurement of televison insertion test signals,
Vol. XII, Rec. 569, ITU, Geneva, 1986.
MONTAGE: PAGE 84 = PAGE BLANCHE
SECTION 3
INTERNATIONAL VIDEOCONFERENCE TRANSMISSIONS
3.1 International videoconference transmissions - Definitions
Recommendation N.81
DEFINITION FOR APPLICATION TO INTERNATIONAL VIDEOCONFERENCE |
TRANSMISSIONS
(under study)
3.2 Line-up, service commissioning and maintenance of video-
conference systems
Recommendation N.86
LINE-UP AND SERVICE COMMISSIONING OF INTERNATIONAL
VIDEOCONFERENCE SYSTEMS OPERATING AT TRANSMISSION BIT RATES
OF 1544 AND 2048 kbit/s
1 General
This Recommendation deals with the line-up and service commis-
sioning of international videoconference systems routed over
transmission paths operating at transmission bit rates of 2048 and
1544 kbit/s. In this context an international videoconference sys-
tem comprises the international videoconference connection and the
videoconference rooms which are interconnected.
Figure 1/N.86 shows the constituent parts of an international
videoconference connection. Recommendation H.110 [1] describes
hypothetical reference connections for videoconferencing.
The video codecs are normally located within the videoconfer-
ence studios but in some circumstances are located elsewhere so
that the local tail serving the videoconference studio may be pro-
vided on wideband analogue (e.g. 5.5 MHz) or higher order digital
transmission systems (e.g. 140 Mbit/s). Codecs are described in
Recommendation H.120 [2].
The location of any 2048/1544 kbit/s remultiplexers which may
be involved will be as agreed between the Administrations.
Figure 1/N.86, p.
Supplement No. 5.2 gives guidance on the setting up and test-
ing arrangements for videoconference studios.
The international videoconference centre provides the inter-
connection point of the national videoconference circuit and the
international link. This interconnection may be made manually or by
automatic means.
Normally the international videoconference link will be common
for all videoconference calls between the two Administrations con-
cerned, whereas the national videoconference circuits will vary
from call to call. Thus, in addition to the setting up and lining
up of the constituent parts of the international videoconference
connection, service commissioning tests are made between video-
conference studios prior to the opening of an international video-
conference service to ensure that a service can be satisfactorily
sustained.
2 Setting up and lining up the constituent parts of the connection
2.1 National videoconference circuits
The national videoconference circuits should be set up and
tested in accordance with the national procedures of the Adminis-
trations concerned. This will include the line up of any sections
which may not be provided as 2048 or 1544 kbit/s digital paths. The
2048 and 1544 kbit/s data performance limits to be met are given in
Table 1/N.86 and it is recommended that two data tests should be
made, each of one hour's duration, on different days and at times
that cover the peak traffic periods on the route concerned.
2.2 International link
The international videoconference link will only need to be
set up and tested when establishing the first service between two
Administrations. The procedures of Recommendation 555 [3] should
apply.
A data test should be made of five hours duration and should
be scheduled so as to include the peak traffic period on the route
concerned. The test results should meet the data performance limits
given in Table 1/N.86.
3 Performance check codec-to-codec
The constituent parts of the connection having been satisfac-
torily lined up and connected together at the international video-
conference centres, three data tests (each of one hour's duration)
should be made between the codecs. The tests should be made on dif-
ferent days and at times to cover the peak traffic periods for the
route. The testers should be connected at the digital line side of
the codecs, as close to the codecs as possible. Each test should
meet the data performance limits given in Table 1/N.86.
Where loop facilities exist, loop measurements may be made in
order to obtain reference measurements for subsequent maintenance.
Care must be taken to avoid simultaneous operation of loop facili-
ties.
H.T. [T1.86]
TABLE 1/N.86
Path performance test limits
| ua)
_________________________________________________________________________________________________________
. {
Nominal data rate | ub)
(kbit/s)
} Bit error ratio (BER) Max. errors in 1 hour {
Severely errored events | uc)
in 1 hour
} {
Error-free seconds
(EFS)
(%)
}
_________________________________________________________________________________________________________
2048 1 x 10DlF2616 7 | 42 0 92
{
1544 1 x 10DlF2616 5 | 30 0 92
_________________________________________________________________________________________________________
2048 1 x 10DlF2616 7 | 42 2 92
{
1544 1 x 10DlF2616 5 | 30 2 92
_________________________________________________________________________________________________________
2048 1 x 10DlF2616 7 | 42 2 92
{
1544 1 x 10DlF2616 5 | 30 2 92
_________________________________________________________________________________________________________
2048 3 x 10DlF2616 21 | 27 2 92
{
1544 3 x 10DlF2616 16 | 89 2 92
_________________________________________________________________________________________________________
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a) The limits are provisional and subject to further study.
b) Structured formatting required with a consequent reduction in
actual test data rate as follows: At 2048 kbit/s, test data rate =
1984 kbit/s (time slots 1 to 31 only); At 1544 kbit/s, test data
rate = 1536 kbit/s (8 bits used for frame alignment).
c) Severely errored events are defined by the particular data tes-
ter used, e.g. 20 | 00 errors in 100 | 00 bits. A continuous period
of up to 10 seconds, during which severely errored transmission
persists, will be considered as a single severely errored event.
Note 1 - In addition to the above limits the BER shall be no worse
than 1 x 10DlF2615 over any 5-minute period during the tests
(5952 errors at 2048 kbit/s and 4608 errors at 1544 kbit/s). If
this test fails, then corrective action shall be taken on the
offending section.
Note 2 - For loop-tests, the above limits should be doubled (92%
EFS becoming 84% EFS).
Table 1/N.86 [T1.86], p.
4 Digital test equipment
The data tester required for the above tests shall be capable
of transmitting and receiving a test pattern within a signal struc-
tured in accordance with Recommendation G.732 [4] for 2048 kbit/s
interfaces or Recommendation G.733 [5] for 1544 kbit/s interfaces.
The nature of the test pattern is undefined but should be the sub-
ject of further study.
When working through a 2048/1544 kbit/s remultiplexer, the
test signal should be restricted to time slots 1-24 with time
slots 25-31 being vacant.
If compatible testers are not available at both ends of the
link or connection under test, then one tester should be used to
transmit and receive with a loop being provided at the other end.
5 Videoconference studios
All videoconference studios that will be used for interna-
tional videoconference calls should comply with agreed design stan-
dards. Providers and operators of such studios are encouraged to
adopt the provisions of Supplement No. 5.2 until CCITT Recommenda-
tions are specified. The adoption of common standards facilitates
the interworking between any pair of studios in different countries
with pre-call adjustments reduced to a minimum.
6 Service commissioning tests
6.1 General
The international videoconference connection having been
satisfactorily tested, functional video and audio service commis-
sioning tests should be undertaken between the videoconference stu-
dios.
6.2 Test videoconference studios
The videoconference studio chosen by an Administration for
commissioning tests should be typical (with regard to the parame-
ters of Supplement 5.2) of all the other studios to be used fo the
service. This studio should then serve as a reference studio for
any future tests between videoconference studios with other
Administrations.
The reference studio for each Administration should be identi-
fied to all other Administrations. The parameters of this studio
should also be shared with all other Administrations.
6.3 Commissioning test
The end-to-end commissioning tests between videoconference
studios are described in Supplement 5.2. The purpose of the tests
is to demonstrate that the international videoconference system
performs adequately when the constituent parts are connected
together. The tests include a subjective assessment of the main
functions of each videoconference studio and selected objective
tests. The tests are not intended to be exhaustive, but should
serve as sample checks in compliance with the standards and as a
confident indicator to both Administrations before the opening of
an internatinal videoconference service.
References
[1] CCITT Recommendation Hypothetical Reference Connections
for Videoconferencing using primary digital group transmission ,
Vol. III, Rec. H.110.
[2] CCITT Recommendation Codecs for videoconferencing using
primary digital group transmission , Vol. III, Rec. H.120.
[3] CCITT Recommendation Bringing international digital
blocks, paths and sections into service , Vol. IV, Rec. M555.
[4] CCITT Recommendation Characteristics of primary PCM
multiplex equipment operating at 2048 kbit/s , Vol. III,
Rec. G.732.
[5] CCITT Recommendation Characteristics of primary PCM
multiplex equipment operating at 1544 kbit/s , Vol. III,
Rec. G.733.
Recommendation N.90
MAINTENANCE OF INTERNATIONAL VIDEOCONFERENCE SYSTEMS
OPERATING AT TRANSMISSION BIT RATES OF 1544 AND 2048 kbit/s
1 Scope
This Recommendation deals with the maintenance procedures to
be applied to international videoconferencing systems operating at
transmission bit rates of 1544 and 2048 kbit/s.
2 General
2.1 The configuration shown in Figure 1/N.90 is a simplified
description of a typical connection.
2.2 Each participating Administration shall establish an
international videoconference centre (IVC) with the same general
responsibilities and functions as those set out in
Recommendation N.55 for an international television centre (ITC) in
respect of international television connections. However, as a
videoconference connection is a bidirectional transmission path,
the choice of control and sub-control IVCs shall always be esta-
blished by mutual agreement. This choice should hold for all the
international videoconference connections serving two Administra-
tions.
Figura 1/N.90, p.
2.3 The maintenance procedures are designed to facilitate res-
toration of service when a videoconference connection is broken, or
unacceptably degraded, during a videoconference call. At this time
it is essential that close cooperation is maintained between con-
trol and sub-control IVCs in order to minimize disruption to the
call.
2.4 The IVCs will require to be provided with equipment such
as codecs, monitors and cameras so as to be able to make limited
functional checks (visual and audio) for confirmation of call
establishment and rapid fault sectionization.
Additionally, testers should be available for 1544 and 2048
kbit/s data performance tests. The testers should be able to send a
structured test signal in accordance with either the
Recommendation G.732 [1] or H.733 [2] structures. The test pattern
should be a pseudo random test signal of sequence length 215DlF2611
as described in Recommendation O.151 [3].
The tester conforming to Recommendation G.733 [2] should be
able to work at 1536 kbit/s information rate, sending the test sig-
nal in time slots 1 to 24.
The tester conforming to Recommendation G.732 [1] should be
able to work at 1536 or 1984 kbit/s information rates. When
switched to 1536 kbit/s it should send the test signal in time
slots 1 to 15 and 17 to 25. When switched to 1984 kbit/s it should
use time slots 1 to 31.
3 Pre-call tests
It is essential that pre-call tests are made to confirm that a
scheduled call will be satisfactory. All equipments and all parts
of the international videoconference connection to be used in a
call should be checked beforehand on the day of the call. For this
purpose tests should be made of the complete transmission path
between the appropriate videoconference studio(s) and frontier
station(s) by each Administration and between the frontier
stations (EF's).
These pre-call tests are intended to be simple checks to
establish that the transmission paths are acceptable, for example,
that the transmitted and received radio frequency carrier levels at
each earth station are within their prescribed limits.
Additionally, where the international videoconference connec-
tion is new or where previous, similar calls have suffered problems
a complete studio-to-studio functional test should be made. This
should take the form of a visual and, if appropriate, audio subjec-
tive assessment of the end-to-end performance. Such tests should be
sufficiently in advance of the start of the call (15 to 30 minutes)
to give some opportunity for clearing any problem which may be
found. As experienced and confidence is gained, the time required
for pre-call testing should reduce.
4 Fault localization
4.1 A general outline of the fault localization procedure for
international videoconference connections is given below. This
approach aims to rapidly localize a fault to a circuit section.
4.2 Fault reports may be received by either IVC on a connec-
tion but shall only be accepted from points within their own coun-
try.
4.3 On receipt of a fault report the IVC shall monitor the
connection where possible to broadly localize the fault unless this
is obvious from the fault report or from other information,
e.g. system alarms. The IVC should then immediately advise the dis-
tant IVC of the reported fault and any information which may assist
to determine the course of action to be taken.
4.4 If the source of the problem is not known then both IVCs
shall work together to determine in which circuit section the fault
lies, e.g. by means of loopback. Preferably this should be in
accordance with an agreed planned procedure. If these procedures do
not localize the fault then the IVCs shall agree the further action
to be taken.
4.5 If at any stage the fault is localized then the appropri-
ate clearance procedures should be put in hand.
4.6 Both IVCs should be in constant telephone contact during
these procedures. The IVCs should report to their respective video-
conference studios (VSs) no longer than 10 minutes after receipt of
the fault report advising on localization progress and estimated
time to restore service. A second status report should be given
after a further maximum period of 10 minutes. If, at 20 minutes
following the fault report, the time to restore service has not
been determined then the customers should be so advised and a deci-
sion made as to whether or not to abort the call.
4.7 If, during localization, the overall connection is found
to be satisfactory, the problem may be caused by the interworking
of the studio equipment (e.g. codecs). In this case it may prove
necessary to monitor and test the connection VS to VS.
4.8 Minor problems that are reported for correction but which
do not make a call unusable, shall be accepted for clearance and
entered in the fault record but shall not count against the service
availability of the connection. Action to deal with such problems
should not interrupt an ongoing call, except at the direction of
the control IVC.
4.9 Where a videoconference call transmission is encrypted,
the VSs shall be required to remove the encryption for fault local-
ization and clearance purposes when requested by the IVCs.
5 Maintenance parameters
5.1 The maintenance limits for 1544 and 2048 kbit/s transmis-
sion paths are given in Table 1/N.90. Where the national video-
conference circuit includes wideband analogue or higher order digi-
tal system sections then the national maintenance standards should
apply to these sections.
5.2 Because of the need to restrict the time taken for dealing
with faults during scheduled videoconference calls, any assessment
of the 1544 and 2048 Kbit/s performance that may be required
should be based on bit error ratio (BER) measurements only. The
measuring time should be kept to the minimum necessary for the
investigation in hand.
5.3 Where maintenance activities do not risk the establishment
or completion of a scheduled videoconference call then any assess-
ment of the 1544 and 2048 kbit/s performance should be against all
the parameters shown in Table 1/N.90. Such measurements should be
made over a minimum period of 15 minutes.
BLANC
H.T. [T1.90]
TABLE 1/N.90
Maintenance limits
| ua)
____________________________________________________________________________________________________________
. {
Nominal data rate | ub)
(kbit/s)
} Bit error ratio (BER) Max. errors in 15 minutes {
Severely errored events | uc)
in 15 minutes
} {
Error-free seconds
(EFS)
(%)
}
____________________________________________________________________________________________________________
1544 1 x 10DlF2616 1382 0 92
{
2048 1 x 10DlF2616 1785 0 92
____________________________________________________________________________________________________________
1544 1 x 10DlF2616 1382 0 92
{
2048 1 x 10DlF2616 1785 0 92
____________________________________________________________________________________________________________
1544 3 x 10DlF2616 4147 0 92
{
2048 3 x 10DlF2616 5357 0 92
____________________________________________________________________________________________________________
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a) The limits are provisional and subject to further study.
b) Structured formatting required with a consequent reduction in
actual test data rate as follows: At 2048 kbit/s, test data rate =
1984 kbit/s (time slots 1 to 31 only); At 1544 kbit/s, test data
rate = 1536 kbit/s (8 bits used for frame alignments).
c) Severely errored events are defined by the particular data tes-
ter used, e.g. 20 | 00 errors in 100 | 00 bits. A continuous period
of up to 10 seconds, during which severely errored transmission
persists, will be considered as a single severely errored event.
Table 1/N.90 [T1.90], p.
References
[1] CCITT Recommendation Characteristics of primary PCM
multiplex equipment operating at 2048 kbit/s , Vol. III,
Rec. G.732.
[2] CCITT Recommendation Characteristics of primary PCM
multiplex equipment operating at 1544 kbit/s , Vol. III,
Rec. G.733.
[3] CCITT Recommendation Error performance measuring equip-
ment for digital systems at the primary bit rate and above ,
Vol. IV, Rec. O.151.
BLANC
MONTAGE: PAGE 92 = PAGE BLANCHE